The turnover of acetylcholine and choline in discrete areas of the brain and in their subcellular pools will be studied in rats. Deuterium-labelled choline will be used to measure both acetylcholine and choline by a pyrolysis gas chromatography method developed by us, in combination with mass fragmentography. Turnover will be studied after making stereotaxic lesions in specific structures in an effort to explore cholinergic pathways. The kinetics of choline transport into different regions of the brain and into synaptosomes will be determined. The effect of an acetylcholine-releasing lipid, recently isolated by us and found only in neural tissue, on turnover will also be studied. As morphine is an antagonist of this lipid, experiments will be conducted to see if, conversely, the lipid is a morphine antagonist.